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fast-export: avoid NULL pointer arithmetic

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Clang 6 reports the following warning, which is turned into an error in a
DEVELOPER build:

	builtin/fast-export.c:162:28: error: performing pointer arithmetic on a null pointer has undefined behavior [-Werror,-Wnull-pointer-arithmetic]
		return ((uint32_t *)NULL) + mark;
		       ~~~~~~~~~~~~~~~~~~ ^
	1 error generated.

The compiler is correct, and the error message speaks for itself.  There
is no need for any undefined operation -- just cast mark to void * or
uint32_t after an intermediate cast to uintptr_t.  That encodes the
integer value into a pointer and later decodes it as intended.

While at it remove an outdated comment -- intptr_t has been used since
ffe659f94d (parse-options: make some arguments optional, add callbacks),
committed in October 2007.

Signed-off-by: Rene Scharfe <l.s.r@web.de>
Acked-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
René Scharfe 2018-05-09 23:06:46 +02:00 committed by Junio C Hamano
parent 27dea4683b
commit c112084af9
1 changed files with 3 additions and 4 deletions
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7
builtin/fast-export.c
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@ -154,15 +154,14 @@ static void anonymize_path(struct strbuf *out, const char *path,
}
}
/* Since intptr_t is C99, we do not use it here */
static inline uint32_t *mark_to_ptr(uint32_t mark)
static inline void *mark_to_ptr(uint32_t mark)
{
return ((uint32_t *)NULL) + mark;
return (void *)(uintptr_t)mark;
}
static inline uint32_t ptr_to_mark(void * mark)
{
return (uint32_t *)mark - (uint32_t *)NULL;
return (uint32_t)(uintptr_t)mark;
}
static inline void mark_object(struct object *object, uint32_t mark)